Should Kerry win and be nominated for a second term in 2008, any chance of Clinton's making her own run for the White House would be put off until at least 2012. She would be 65 and a whole new crop of presidential contenders could be on the scene.
But a rousing speech for Kerry could also help position Clinton for a presidential run in 2008 if Kerry fails to knock George W. Bush from the White House.
"That's not going to happen," she said during a visit Friday to Troy, N.Y. "We are going to win in November and I am going to be campaigning for John Kerry and John Edwards in 2008 for a second term."
She said Monday she will talk about both Bill Clinton (search) and Kerry in her convention speech introducing her husband.
"What I want to do is talk about John Kerry," she said on NBC's "Today" show. "I think he is exactly the right person to be president at this time."
Clinton dismissed talk she's the front-runner among the party's presidential candidates-in-waiting should Kerry falter. "I have been the subject of so many wonderful theories ever since my husband began running for president in 1991," she said Monday.
Still, many party leaders consider her just that.
"People will endlessly turn over Hillary Clinton's remarks for what's there and what's intended and what people think was intended," said Steve Grossman, who served as a Democratic national chairman under President Clinton.
But Grossman, like many others in the Clinton camp, insists Clinton and her husband, the former president, will be working all-out to elect Kerry.
"You cannot underestimate how focused she is on getting George Bush and Dick Cheney out of the White House, and turning the Senate Democratic," said Clinton media consultant Mandy Grunwald.
"I think she'd be happy to never be president if she could get these guys out of the White House," Grunwald added.
That is the party line. Veteran independent pollster Lee Miringoff said Hillary Clinton has no choice but to stick with it.
"She has to be totally enthusiastic" about the Kerry ticket, said Miringoff, head of Marist College's Institute for Public Opinion in Poughkeepsie, N.Y.
"Is she going to work hard for this campaign? Absolutely. And, will everybody know it? Absolutely," said former New York Gov. Mario Cuomo, who in 1988 and 1992 was a front-running Democratic presidential candidate-in-waiting who didn't run. "Would you know it if she didn't? You could tell right away."
"It is something she has to be sensitive to because people do see her as being in the wings, looking to make a run at some point," said Gail Shaffer, a New York delegate pledged to Sen. John Edwards, Kerry's running mate.
Kerry's choice of Edwards sets up a potential 2008 rivalry between the North Carolina Democrat and the former first lady. In jockeying for possible position, Edwards doesn't have to do anything and Clinton can't be seen as doing anything, said Shaffer, who was Cuomo's secretary of state.
"He already ran for president. He's been very overt," said Shaffer. "She has to walk more of a delicate tightrope."
With his and hers best-selling books, both Clintons have been getting attention lately. Some Democrats worried that the former president's just-published book, "My Life," would cast a shadow over the Kerry campaign with reminders of the Monica Lewinsky affair.
While Hillary Clinton has sought to avoid any sign of tension between her and Kerry, the waters were roiled two weeks ago when the Kerry campaign announced the prime-time speakers' lineup for the convention and her name was missing.
The Kerry camp said it was simply a case of the former first lady not having asked to speak, and other Democrats sought to brush the controversy aside.
"It's not even a tempest in a teapot. It's a tempest in a teacup," said New York Attorney General Eliot Spitzer. "It's one of those little side stories that we all will forget by the time of the convention."
Cuomo's advice to Clinton?
"All you need to do is address the issue very candidly and honestly," said Cuomo, who famously loved to keep people guessing on the subject. "The truth is, she was the most popular Democrat before we picked the candidate. The truth is, she is an extremely popular candidate now."